Just using DND would still leave the call queueing. Another option here would be to have the last user in the huntgroup set to a fictitous user, which forwards unconditionally (and huntgroup calls) to the other huntgroup. This would then go through each user, but wouldn't matter if they're on DND or logged out, and lastly forward to the second huntgroup. It would take only up to a few seconds (depending on how many users are in the primary huntgroup) to forward.